One of the aims is to have a difference in "important" and less important towers. On a good topographical map you want to show big transmitters on mountains or huge telecommunications towers in a big city due to being a great landmark, whereas less noticeable mobile phone base stations may be noise on a topographical map (although still immensely useful for things like wireless positioning). As you can see, a difference between base stations mounted on a tower or just mounted on a roof is made.

Advanced tagging of mobile phone base stations

You can add more information to the base stations, but remember: Only add information you know for sure.
Please try to avoid the use of e.g. operator=T-Mobile, use MNC=01 instead.[1]